1. Field of the Invention
The present invention relates to a monopulse radio tracking system, and more particularly to a monopulse system operable in a multiple source environment.
2. Description of the Prior Art
Monopulse radio tracking systems have been known and utilized in the prior art for direction finding and for guidance of missiles to intercept active or passive targets. A typical system uses four horn antennas where signals are combined to produce sum and difference signals. These signals are processed in a superheterodyne circuit to produce a sum IF signal, and azimuth and elevation difference IF signals. The IF signals are detected and processed to obtain a measure of the angular displacement of a source signal from the boresight of the antenna. In a tracking system, the measure thus derived is utilized to generate servo control signals causing the antenna boresight to become aligned with the source signal. Such prior art tracking systems are satisfactory when a single source or target is within the antenna beamwidth; however, when multiple targets are present and within the antenna beamwidth, known prior art systems cannot discriminate among such multiple targets. In general, a typical monopulse system will track the weighted power centroid of the multiple sources. Consequently, a missile control system based on prior art tracking systems will cause the vehicle to pass between multiple targets.